“Giant mastodons are the best mastodons”

Site excavations have established that Paleo-Indians hunted the American mastodon here during the ice age. The site is the home of the Kimmswick Bone Bed, one of the most famous and extensive Pleistocene ice age deposits of fossils, including a number of bones of giant mastodons. The museum displays artifacts, fossils and a replica of a mastodon skeleton, and outlines the story of the Clovis culture, which existed in the area between 10,000 and 14,000 years ago.
Open for day use, the site offers picnicking and hiking.
Museum admission: $4, ages 6-12 $2.50, younger than 6, free. Grounds are free.
Located 20 miles south of St. Louis, off I-55, at exit 186.

Has hiking trails and a creek that you can cool off and swim in. I never saw it advertised anywhere, however there were lots of people that were there the day we went. Shallow creek that was shaded and had really clear water so it was good for the kids to wade in.